This invention relates to dielectric compositions, and more particularly to an improved high dielectric constant low fire composition capable of achieving the EIA rating of Y5V.
The U.S. Pat. No. 5,361,187, which is assigned to the same assignee as the present application, discloses ceramic dielectric compositions which are capable of meeting both Z5U and Y5V standards or ratings determined by the U.S. Electronics Industries Association (EIA). Such compositions are particularly suitable for use in the manufacture of high dielectric constant multi-layer ceramic capacitors (MLCC's) which have very high insulation resistance capacitance (RC), for instance above about 10,000 ohm-farads at 25.degree. C., and above about 1,000 ohm-farads at 85.degree. C. Moreover, for those compositions having Y5V rating the temperature coefficient of capacitance (TCC) characteristics are within +22 to -82% over a temperature range of -30.degree. to 85.degree. C.
Referring to Table III in the above-noted U.S. patent, it will be noted that multi-layer ceramic capacitors made from samples 1 to 12 and 40 exhibited Y5V characteristics. These characteristics were achieved by adding various combinations of dopants, such as oxides of Y, La, Zr, Nb and Mn to variations of a base formulation (Ba.sub.1-x Ca.sub.x) (Ti.sub.1-y-z SnyZrz)O.sub.3. Notably, however, the compositions disclosed in the above-noted patent are high fire formulations which do not include any low melting point glass frit or network formers such as SiO.sub.2, B.sub.2 O.sub.3 and GeO.sub.2, nor do they employ any low melting elements such as lead, lithium and bismuth. However, there is a need for providing a low fire Y5V type dielectric material which not only will maintain the Y5V characteristics, but also will exhibit a high dielectric constant (K.sub.RT).
It is an object of this invention heretofore, to provide an improved dielectric composition which not only maintains Y5V characteristics, but likewise constitutes a relatively low fire dielectric material which is capable of exhibiting a very high dielectric constant.
A further object of this invention is to provide a novel Y5V dielectric composition having incorporated therein glass network forming elements such as SiO.sub.2, GeO.sub.2 and B.sub.2 O.sub.3, and/or low melting elements such as lead, lithium and bismuth.
A more specific object of this invention is to provide an improved Y5V dielectric material which has incorporated therein a low melting glass composition, such as for example a lead boro alumino silicate frit that is produced by Ferro Corporation under the designation Ferro EGD2765.
Other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims.